This invention is directed to silicon oxide alloy nanoparticles. The silicon oxide alloys are obtained by laser ablation of a silicon target and a target of a metal in an oxygen containing atmosphere. The morphology of the obtained silicon oxide alloy consists of nanoparticles about 5-50 nanometers (nm) in diameter, preferably about 10-20 nanometers. The nanoparticles are fused together (i.e., agglomerated) into an open three-dimensional network which is porous and has a high surface area.
The synthesis and characterization of nanoparticles has received attention in recent years for their use as catalysts. A range of nanoparticles has been produced by chemical and physical methods. The most common physical methods involve gas condensation techniques, where oven sources are used to produce metal vapors. In spite of success with these methods, there are still problems and limitations, such as (i) reactions between metal vapors and oven materials, (ii) inhomogeneous heating of the source, which limits control of particle size and distribution, (iii) incomplete vaporization of refractory metals due to low vapor pressure, (iv) limited control of aggregation, and (v) range of control of composition of mixed metal particles due to differences in composition between the alloys and mixed vapors.
The advantages over other heating methods which laser vaporization techniques provide are (i.) the production of high density metal vapor within a short period of time, i.e. 10.sup.-8 s, (ii) the generation of directional high speed metal vapor from a solid target for directional deposition of the particles, (iii) control of evaporation from specific spots on a target, and (iv) simultaneous or sequential evaporation of several different targets. Some of these advantages have been demonstrated in the synthesis of ultra-fine metal particles, but control of the nucleation process, which strongly affects particle size, composition, and morphology of the deposited material, has not yet been achieved.
What we discovered, however, is a new form of certain silicon oxide alloys in which nanoparticles of a silicon oxide metal oxide alloy aggregate into unique web microstructures. One of the nanoparticle silicon oxide alloys, i.e. the oxide of SiAl, emits a medium to strong white photoluminescence with a bluish tint, upon irradiation with blue light (i.e., about 430 nm) or ultraviolet light (i.e., about 230-360 nm). These web structured nanoparticle silicon oxide alloys have a controllable size and composition, and are synthesized by a technique combining advantages of pulsed laser vaporization, and controlled condensation in a diffusion cloud chamber, under well defined conditions of temperature and pressure.
We found that the SiPt nanoparticle oxide alloy is useful in catalysis. Its advantages in catalysis are its high surface area and high temperature stability. The SiMo and the SiAl nanoparticle oxide alloys are useful in modifying the photoluminescent properties of silica nanoparticles, as we determined that alloying changes the intensity and the wavelength of the emitted light. The SiAl nanoparticle oxide alloy is also suitable for its luminescence in applications where silica is used in semiconductor manufacture.